Since time immemorial, people have lived with others side by side. Thus, communication is indispensable for humankind. That is, it is no exaggeration to say that the history of humankind is the history of communication. Communication tools have been changing with the times.
Communication tools had previously been used in long-distance communication that cannot be made face-to-face. Specifically, in the distant past, beacons and the like were used as a communication tool. Thereafter, wire telephones and the like appeared. In recent years with technologies advanced, wireless cellular phones and the like have been used.
In addition, also in a short distance in which a face-to-face meeting is possible, in order to make communication other than verbal one, cellular phones with an infrared function have come to be used as a communication tool (see Patent Document 1, for example). That is, a user of a cellular phone performs infrared communication by bringing the cellular phone close to a cellular phone of another person, thereby being able to make communication with the other person such as exchanging information like e-mail addresses with the other person.